Vertical cavity surface emitting laser and laser equipment
By setting up a convex curved surface structure on the cap layer, the problem of large divergence angle of the vertical cavity surface emission laser is solved, and the effect of reducing divergence angle and reducing costs is achieved.
Patent Information
- Application Number
- CN202421523581.2
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- Filing Date
- 2024-07-01
- Publication Date
- 2025-03-21
- Estimated Expiration
- 2034-07-01
AI Technical Summary
现有垂直腔面发射激光器的发散角较大,导致需要增加准直透镜,增加了成本和体积。
The convex curved surface structure is arranged on the cap layer to reduce the divergence angle through transmission, avoiding the need to add additional collimation lenses.
The divergence angle of the vertical cavity surface emitting laser is effectively reduced, and the cost and volume of the entire laser is reduced.
Smart Images
Figure CN222654558U_ABST
Abstract
Description
Technical Field
[0001] The present application relates to the field of laser technology, and in particular to a vertical cavity surface emitting laser and a laser device. Background Art
[0002] Vertical-Cavity Surface-Emitting Laser (VCSEL) is a semiconductor whose laser is emitted perpendicular to the top surface, which is different from the edge-emitting laser that is generally produced by cutting independent chips and emitting laser from the edge.
[0003] At present, for vertical cavity surface emitting lasers, the divergence angle is relatively large. In order to reduce the divergence angle, it is generally necessary to add a collimating lens, but adding a collimating lens will increase the cost and volume of the entire laser.
[0004] In summary, the existing technology has the problem of a large divergence angle of the laser. Utility Model Content
[0005] The purpose of the present application is to provide a vertical cavity surface emitting laser and a laser device to solve the problem of large divergence angle of the laser in the prior art.
[0006] In order to achieve the above purpose, the technical solution adopted in the embodiment of the present application is as follows:
[0007] On the one hand, an embodiment of the present application provides a vertical cavity surface emitting laser, which includes an N-type electrode, a P-type electrode, an optical structure and a cap layer, wherein the N-type electrode is connected to the bottom surface of the optical structure, the cap layer is connected to the top surface of the optical structure, the P-type electrode is connected to the top outer side of the cap layer, and the top middle area of the cap layer is set as a convex curved surface structure, and the convex curved surface structure is used to reduce the divergence angle of the vertical cavity surface emitting laser.
[0008] Optionally, the height of the middle area of the convex curved surface structure is the largest, and the optical thickness of the convex curved surface structure is related to the phase matching thickness of the cap layer; wherein the phase matching thickness is used to characterize the optical thickness corresponding to the maximum reflectivity.
[0009] Optionally, in the convex curved surface structure, the optical thickness of the middle region is greater than the phase matching thickness of the cap layer, and the optical thickness of the edge region is less than the phase matching thickness of the cap layer.
[0010] Optionally, the optical thickness of the convex curved surface structure is 0.5nλ-0.12λ to 0.5nλ+0.12λ from the edge area to the middle area, wherein λ is the wavelength of light emitted by the optical structure and n is an integer.
[0011] Optionally, the cap layer also includes a main structure, a groove is set in the middle position of the main structure, the convex curved surface structure is located in the groove of the main structure and is integrally formed with the main structure; the P-type electrode is located on the table of the main structure.
[0012] Optionally, the tangent inclination angles at different positions on the convex curved surface structure satisfy the formula:
[0013] n1sin(α-θ1)=n2sinα
[0014] Among them, n1 represents the refractive index of the cap layer, n2 represents the refractive index of air, α represents the tangent inclination angle of the convex surface structure, and θ1 represents the angle between the incident light at different positions and the vertical direction.
[0015] Optionally, the optical structure includes a substrate, an N-type reflector, a P-type reflector, a resonant cavity and a quantum well layer, the quantum well layer is located in the resonant cavity, and the substrate, the N-type reflector, the resonant cavity, the P-type reflector and the cap layer are arranged layer by layer.
[0016] Optionally, the optical structure further includes an oxide layer, the oxide layer is located between the resonant cavity and the P-type reflector, and a middle area of the oxide layer is hollowed out.
[0017] Optionally, the cap layer is made of GaAs, SiN or SiOx material.
[0018] On the other hand, an embodiment of the present application further provides a laser device, which includes the above-mentioned vertical cavity surface emitting laser.
[0019] Compared with the prior art, this application has the following beneficial effects:
[0020] The present application provides a vertical cavity surface emitting laser and a laser device, the vertical cavity surface emitting laser includes an N-type electrode, a P-type electrode, an optical structure and a cap layer, the N-type electrode is connected to the bottom surface of the optical structure, the cap layer is connected to the top surface of the optical structure, the P-type electrode is connected to the top outer side of the cap layer, and the top middle area of the cap layer is set as a convex curved surface structure, and the convex curved surface structure is used to reduce the divergence angle of the vertical cavity surface emitting laser. Since the present application directly sets a convex curved surface structure in the cap layer, the light emitted by the light-emitting structure can reduce the divergence angle through the transmission effect of the convex curved surface structure. In addition, since only a convex curved surface structure needs to be set on the cap layer, there is no need to set a redundant collimating lens structure, thereby reducing the cost and volume of the entire laser.
[0021] In order to make the above-mentioned objects, features and advantages of the present application more obvious and easy to understand, preferred embodiments are specifically cited below and described in detail with reference to the attached drawings. BRIEF DESCRIPTION OF THE DRAWINGS
[0022] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings required for use in the embodiments will be briefly introduced below. It should be understood that the following drawings only show certain embodiments of the present application and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other related drawings can be obtained based on these drawings without paying creative work.
[0023] Figure 1 It is a schematic diagram of the structure of a vertical cavity surface emitting laser in the prior art.
[0024] Figure 2 A schematic diagram of the structure of a vertical cavity surface emitting laser provided in an embodiment of the present application.
[0025] Figure 3 Schematic diagram of the effect of the change in the optical thickness of the cap layer on the overall reflectivity.
[0026] Figure 4 Schematic diagram of the optical path of a vertical cavity surface emitting laser in the prior art.
[0027] Figure 5 A schematic diagram of the optical path of a vertical cavity surface emitting laser provided in an embodiment of the present application.
[0028] Figure 6 A curve diagram showing the relationship between the tangent inclination angle at the corresponding position of the divergence angle of the convex surface provided in an embodiment of the present application and the divergence angle under normal circumstances.
[0029] In the figure:
[0030] 110 - N-type electrode; 120 - P-type electrode; 130 - cap layer; 141 - substrate; 142 - N-type reflector; 143 - resonant cavity; 144 - quantum well layer; 145 - P-type reflector; 146 - oxide layer. DETAILED DESCRIPTION
[0031] In order to make the purpose, technical solution and advantages of the embodiments of the present application clearer, the technical solution in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are part of the embodiments of the present application, rather than all the embodiments. The components of the embodiments of the present application described and shown in the drawings here can be arranged and designed in various different configurations.
[0032] Therefore, the following detailed description of the embodiments of the present application provided in the accompanying drawings is not intended to limit the scope of the present application for which protection is sought, but merely represents selected embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in the field without creative work are within the scope of protection of the present application.
[0033] It should be noted that similar reference numerals and letters represent similar items in the following drawings, so once an item is defined in one drawing, it does not need to be further defined and explained in subsequent drawings. At the same time, in the description of this application, the terms "first", "second", etc. are only used to distinguish the description and cannot be understood as indicating or implying relative importance.
[0034] It should be noted that, in this document, relational terms such as first and second, etc. are merely used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any actual relationship or order between these entities or operations.
[0035] In the description of the present application, it should be noted that the terms "upper", "lower", "inside", "outside", etc. indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, or are the orientations or positional relationships in which the product of the application is usually placed when in use. They are only for the convenience of describing the present application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as a limitation on the present application.
[0036] In conjunction with the accompanying drawings, some embodiments of the present application are described in detail below. In the absence of conflict, the following embodiments and features in the embodiments can be combined with each other.
[0037] As described in the background art, in the prior art, the divergence angle of a vertical cavity surface emitting laser is generally large, and therefore it is necessary to reduce the divergence angle of the laser.
[0038] As an implementation, see Figure 1 In order to reduce the divergence angle of the laser, an optical collimating lens can be installed on the outside of the laser, such as a traditional lens or a new lens such as a metasurface. By setting a collimating lens, the light beam emitted by the VCSEL chip at a certain angle to the vertical direction can be collimated into a light beam parallel to the vertical direction, thereby reducing the divergence angle of the device.
[0039] As another implementation method, the divergence angle can be reduced by increasing the length of the resonant cavity.
[0040] However, the method of adding an optical collimating lens will increase the cost and the overall size, which is not conducive to miniaturization. As for the method of increasing the length of the resonant cavity, the divergence angle is mainly reduced by the angle of the impact mode, but the degree of reduction of the divergence angle is relatively limited.
[0041] In view of this, in order to solve the above problems, an embodiment of the present application provides a vertical cavity surface emitting laser, which achieves the purpose of reducing the divergence angle by providing a curved surface structure on the cap layer.
[0042] The vertical cavity surface emitting laser provided in this application is exemplarily described below:
[0043] As an alternative implementation, see Figure 2 The vertical cavity surface emitting laser includes an N-type electrode 110, a P-type electrode 120, an optical structure and a cap layer 130. The N-type electrode 110 is connected to the bottom surface of the optical structure, the cap layer 130 is connected to the top surface of the optical structure, the P-type electrode 120 is connected to the top outer side of the cap layer 130, and the top middle area of the cap layer 130 is set as a convex curved surface structure, which is used to reduce the divergence angle of the vertical cavity surface emitting laser.
[0044] Since the present application directly sets a convex curved surface structure in the cap layer 130, the light emitted by the light-emitting structure can reduce the divergence angle through the transmission effect of the convex curved surface structure. At the same time, the present application only needs to set a convex curved surface structure on the cap layer 130, so there is no need to set up an extra collimating lens structure, etc., thereby reducing the cost and volume of the entire laser.
[0045] The optical structure includes a substrate 141, an N-type reflector 142, a P-type reflector 145, a resonant cavity 143, and a quantum well layer 144. The quantum well layer 144 is located in the resonant cavity 143. The substrate 141, the N-type reflector 142, the resonant cavity 143, the P-type reflector 145, and the cap layer 130 are arranged layer by layer. The optical structure also includes an oxide layer 146, which is located between the resonant cavity 143 and the P-type reflector 145, and the middle area of the oxide layer 146 is hollowed out. Of course, when making the optical structure, the specific size of the middle hollow area of the oxide layer 146 can be determined as needed.
[0046] It should be noted that when making an oxide layer, the oxide layer to be oxidized is actually oxidized along the periphery toward the central area. Therefore, the oxide layer described in this application is located in the peripheral area; and the hollow area described in this application refers to the unoxidized area in the middle. In practical applications, the size of the unoxidized area can be adjusted according to the needs of the laser.
[0047] Among them, the substrate 141 is used to carry the entire chip structure and connect the power supply. The N-type reflector 142 and the P-type reflector 145 can both play the role of emitting light beams, so that the light beams are continuously reflected back and forth between the N-type reflector 142 and the P-type reflector 145. The resonant cavity 143 is the resonance area of the excitation light and the reflected light, which plays the role of selecting the wavelength. After being energized, the quantum well layer 144 converts electrical energy into light energy and can excite light in a certain wavelength range. The cap layer 130 is a layer for realizing phase modulation and making special structures, which is generally a gallium arsenide material. Of course, materials such as SiN or SiOx can also be used, which is not limited here. In addition, the optical structure also includes an oxide layer 146, which is located between the resonant cavity 143 and the P-type reflector 145, and the middle area of the oxide layer 146 is hollowed out. Due to the difference in refractive index and conductivity, the oxide layer 146 can achieve the limitation of current and light field.
[0048] Therefore, the working principle of the optical structure provided by this application is:
[0049] After power is turned on, the quantum well layer 144 generates excitation light, and the excitation light is continuously reflected back and forth by the N-type reflector 142 and the P-type reflector 145 to form reflected light. The reflected light resonates with the excitation light in the resonant cavity 143, and finally outputs high-power light.
[0050] After the optical structure emits light, the light propagates through the convex curved surface structure, and then the refraction effect between the convex curved surface structure and the air can be used to reduce the divergence angle of the entire laser.
[0051] exist Figure 2 In the figure, the reference line of the convex curved surface structure is the dotted line mark in the figure, and the dotted line position is the phase matching thickness of the cap layer. It should be noted that the phase matching thickness of the cap layer described in this application actually refers to the position where the entire P-type reflector 145 and the cap layer 130 structure achieve phase matching (In-phase) together (that is, the reflectivity reaches the maximum value at this time). Since the optical thickness of the cap layer 130 has a greater impact on the overall reflectivity, it is necessary to limit the thickness of this area.
[0052] like Figure 3 As shown in FIG. 1 , the effect of the change in the optical thickness of the cap layer 130 on the overall reflectivity is shown in FIG. 1 . In the figure, the phase matching position is when the optical thickness of the cap layer 130 is an integer multiple of 0.5 times the wavelength. Figure 3It can also be seen that when the thickness of the cap layer 130 is within a certain range of 0.5 times the wavelength thickness, the reflectivity value changes relatively little, which has little effect on the laser lasing and is acceptable. However, if it exceeds this range, the laser lasing will be significantly affected. Therefore, the height of the protrusion at the center of the spherical surface and the depth of the surrounding depression should be within a certain optical thickness above and below the phase matching line within a certain radius from the center to the edge (surface spot coverage range) to ensure a higher optical reflectivity and a smaller optical loss.
[0053] On this basis, the optical thickness of the convex surface structure is related to the phase matching thickness of the cap layer. Specifically, Figure 2 The optical thickness of the convex surface structure is located near the dotted line in the figure.
[0054] In the first implementation, the optical thickness of the convex curved surface structure may be higher than the thickness at the dotted line mark, that is, the optical thickness of the middle region and the optical thickness of the edge region are both higher than the phase matching thickness of the cap layer. In the first implementation, the optical thickness of the convex curved surface structure may be lower than the thickness at the dotted line mark, that is, the optical thickness of the middle region and the optical thickness of the edge region are both lower than the phase matching thickness of the cap layer. In the third implementation, the optical thickness of the convex curved surface structure may include the thickness at the dotted line mark, that is, the optical thickness of the middle region is greater than the phase matching thickness of the cap layer, and the optical thickness of the edge region is less than the phase matching thickness of the cap layer.
[0055] As an implementation method, the optical thickness of the convex curved surface structure is 0.5nλ-0.12λ to 0.5nλ+0.12λ from the edge region to the middle region, where λ is the wavelength of light emitted by the optical structure and n is an integer. For example, the optical thickness of the convex curved surface structure is 0.5λ-0.12λ to 0.5λ+0.12λ from the edge region to the middle region, and at this time, the phase matching thickness of the cap layer is 0.5λ.
[0056] By setting the optical thickness of the convex curved surface structure provided in the present application, it is possible to ensure that the reflectivity in the vertical cavity surface emitting laser is high and the performance is better.
[0057] Furthermore, with respect to the width of the convex curved surface structure, the width of the convex curved surface structure of the present application is greater than the coverage width of the surface light spot.
[0058] As for the cap layer 130 structure, the cap layer 130 also includes a main structure, a groove is set in the middle position of the main structure, the convex curved surface structure is located in the groove of the main structure, and is formed integrally with the main structure; the P-type electrode 120 is located on the table of the main structure. Through the setting of this structure, the convex curved surface structure can be directly processed on the cap layer 130 without adding additional structures, which can achieve the purpose of reducing costs.
[0059] When current is applied through the electrodes, the light beam of the vertical cavity surface emitting laser will pass through the central convex surface area. At this time, due to the difference in refractive index between the material of the cap layer 130 and the refractive index of the air, the surface refracts the light beam. According to Snell's refraction law, n1*sinθ1=n2*sinθ2, the divergence angle of the light beam emitted into the free space can be calculated, where n1 represents the refractive index of the cap layer 130, n2 represents the refractive index of the air, θ1 represents the angle between the incident light beam and the vertical direction, and θ2 represents the angle between the outgoing light beam and the vertical direction.
[0060] On this basis, see Figure 4 and Figure 5 In the figure, the dotted line is parallel to the vertical direction. Figure 5 In the figure, the tangent inclination angle of the convex curved surface structure is α. That is, the angle between the tangent line of the convex curved surface structure and the horizontal line. The arrow line is the incident light of the excitation light on the upper surface (or convex curved surface), and is output through the cap layer 130 to form an outgoing light. For two devices that are identical except for the surface structure, the inclination angle of the incident light relative to the vertical line is consistent, which is θ1, and the outgoing angle θ2 is 1 / 2 of the laser beam divergence angle in the normal case. Figure 4 and Figure 5 By comparison, we can see that Figure 5 The structure shown can effectively reduce the light divergence angle of the vertical cavity surface emitting laser.
[0061] Furthermore, in order to make the laser beam of the convex curved surface structure of the present application close to collimation, the angle between the emitted light and the vertical line needs to be 0, and the emission angle at this time is α. According to the Snell refraction formula, the following formula can be obtained:
[0062] n1sin(α-θ1)=n2sinα
[0063] Wherein, n1 represents the refractive index of the cap layer 130, n2 represents the refractive index of air, α represents the tangent inclination angle of the convex curved surface structure, and θ1 represents the angle between the incident light and the vertical direction.
[0064] That is, when the tangent inclination angle of the convex curved surface structure satisfies the above formula, the light emitted by the vertical cavity surface emitting laser can be collimated without the need for an additional collimating lens, thereby achieving beam collimation at a low cost.
[0065] This formula can obtain the relationship between the tangent inclination angle α and θ1 of the convex surface. For the vertical cavity surface emitting laser, the angle between the incident light and the vertical direction is different at different light-emitting positions, and in the middle area, the value of θ1 is 0, which is the smallest angle; in the direction from the middle area to the edge areas on both sides, the value of θ1 gradually increases, and accordingly, the tangent inclination angle of the convex surface structure also gradually increases.
[0066] Therefore, based on the measurable θ1, the corresponding tangent inclination angles at each position of the convex surface can be designed to achieve the purpose of collimating or nearly collimating the laser beam. Figure 6 The curve shows the relationship between the tangent inclination angle α at the corresponding position of the convex surface divergence angle and the divergence angle in the normal situation. The divergence angle of the convex surface is θ1.
[0067] Based on the above implementation, an embodiment of the present application further provides a laser device, which includes the above vertical cavity surface emitting laser.
[0068] In summary, the present application provides a vertical cavity surface emitting laser and a laser device, the vertical cavity surface emitting laser includes an N-type electrode, a P-type electrode, an optical structure and a cap layer, the N-type electrode is connected to the bottom surface of the optical structure, the cap layer is connected to the top surface of the optical structure, the P-type electrode is connected to the top outer side of the cap layer, and the top middle area of the cap layer is set as a convex curved surface structure, and the convex curved surface structure is used to reduce the divergence angle of the vertical cavity surface emitting laser. Since the present application directly sets a convex curved surface structure in the cap layer, the light emitted by the light-emitting structure can reduce the divergence angle through the transmission effect of the convex curved surface structure. In addition, since only a convex curved surface structure needs to be set on the cap layer, there is no need to set a redundant collimating lens structure, thereby reducing the cost and volume of the entire laser.
[0069] The above description is only the preferred embodiment of the present application and is not intended to limit the present application. For those skilled in the art, the present application may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.
[0070] It will be apparent to those skilled in the art that the present application is not limited to the details of the exemplary embodiments described above, and that the present application can be implemented in other specific forms without departing from the spirit or essential features of the present application. Therefore, the embodiments should be considered exemplary and non-limiting in all respects, and the scope of the present application is defined by the appended claims rather than the above description, and it is intended that all changes falling within the meaning and scope of the equivalent elements of the claims be included in the present application. Any reference numeral in a claim should not be considered as limiting the claim to which it relates.
Claims
1. A vertical cavity surface emitting laser, characterized in that: The vertical cavity surface emitting laser includes an N-type electrode, a P-type electrode, an optical structure and a cap layer, the N-type electrode is connected to the bottom surface of the optical structure, the cap layer is connected to the top surface of the optical structure, the P-type electrode is connected to the top outer side of the cap layer, and the top middle area of the cap layer is set as a convex curved surface structure, and the convex curved surface structure is used to reduce the divergence angle of the vertical cavity surface emitting laser.
2. The vertical cavity surface emitting laser according to claim 1, characterized in that: The middle area of the convex curved surface structure has the largest height, and the optical thickness of the convex curved surface structure is related to the phase matching thickness of the cap layer; wherein the phase matching thickness is used to characterize the optical thickness corresponding to the maximum reflectivity.
3. The vertical cavity surface emitting laser according to claim 2, characterized in that: In the convex curved surface structure, the optical thickness of the middle region is greater than the phase matching thickness of the cap layer, and the optical thickness of the edge region is less than the phase matching thickness of the cap layer.
4. The vertical cavity surface emitting laser according to claim 2, characterized in that: The optical thickness of the convex curved surface structure is 0.5nλ-0.12λ to 0.5nλ+0.12λ from the edge area to the middle area, wherein λ is the wavelength of light emitted by the optical structure and n is an integer.
5. The vertical cavity surface emitting laser according to claim 1, characterized in that: The cap layer also includes a main body structure, a groove is arranged in the middle of the main body structure, the convex curved surface structure is located in the groove of the main body structure and is integrally formed with the main body structure; the P-type electrode is located on the table of the main body structure.
6. The vertical cavity surface emitting laser according to claim 1, characterized in that: The tangent inclination angles at different positions on the convex surface structure satisfy the formula: n1sin(α-θ1)=n2sinα Among them, n1 represents the refractive index of the cap layer, n2 represents the refractive index of air, α represents the tangent inclination angle of the convex surface structure, and θ1 represents the angle between the incident light at different positions and the vertical direction.
7. The vertical cavity surface emitting laser according to claim 1, characterized in that: The optical structure includes a substrate, an N-type reflector, a P-type reflector, a resonant cavity and a quantum well layer, wherein the quantum well layer is located in the resonant cavity, and the substrate, the N-type reflector, the resonant cavity, the P-type reflector and the cap layer are arranged layer by layer.
8. The vertical cavity surface emitting laser according to claim 7, characterized in that: The optical structure also includes an oxide layer, which is located between the resonant cavity and the P-type reflector, and a middle area of the oxide layer is hollowed out.
9. The vertical cavity surface emitting laser according to claim 1, characterized in that: The cap layer is made of GaAs, SiN or SiOx material.
10. A laser device, characterized in that: The laser device comprises the vertical cavity surface emitting laser according to any one of claims 1 to 9.